Climate change led to mass immigration to America in 19th century, study finds

FREIBURG, Germany — A significant portion of the American population can trace at least part of their ancestry back to Germany. In the 19th century, millions of people from southwest Germany emigrated to the U.S., partially because of political turmoil: wars, revolutions, and a century of poverty. But a new study leads scientists to believe that climate change motivated a major portion of this segment to move to America, too.

It’s estimated that 5 million Germans moved to America in the 19th century. Modern Germany wasn’t officially founded as one country until the 1830s, and many in the area wanted to escape violence and political persecution. But researchers from the University of Freiburg say the 19th century was also known as the Little Ice Age in Europe, because of glacial advances in the Alps, and several unusually cold winters and cool summers. The century also saw several extreme weather events such as droughts and floods, and the authors believe those events played a significant role in immigration.

“Overall, we found that climate indirectly explains up to 20-30% of migration from Southwest Germany to North America in the 19^th century,” says Rüdiger Glaser, lead author of the study and a professor at the university, in a news release. “The chain of effects is clearly visible: poor climate conditions lead to low crop yields, rising cereal prices and finally emigration. But it is only one piece of the puzzle.”

The research team compared official migration statistics and population data with weather data, harvest yields, and the prices of cereal grains during this time, focusing on the region that is now the state of Baden-Württemberg, where many of the migrants, including Charles Pfizer of pharmaceutical fortune and fame, came from.

The researchers found that the first major wave of immigration from this state came around 1816, dubbed the “year without summer” because of declining temperatures in the region. These low temperatures are believed to be the result of the eruption of Mt. Tambora in Indonesia, which spewed huge amounts of volcanic ash gases into the atmosphere, affecting the climate worldwide.

While climate analyses explained other waves of migration from the German state, it didn’t appear to be as large of a factor driving the biggest wave from Germany between 1850 and 1855. The climate did lead to low harvest numbers around this time, while other factors, such as France banning food exports, drove up food prices. The German government even paid some of its poorest Baden residents to leave the country to save on welfare and lower the risk of popular uprisings.

“Migration in the 19^th century was a complex process influenced by multiple factors. Lack of economic perspectives, social pressure, population development, religious and political disputes, warfare, family ties and the promotion of emigration from different sides influenced people’s decision to leave their home country,” says Glaser. “Nevertheless, we see clearly that climate was a major factor.”

The full study was published on Nov. 21, 2017 in Climate of the Past, an interactive, open-access journal of the European Geosciences Union.